Method of making alkyl lead compounds

ABSTRACT

A METHOD OF MAKING ALKYL LEAD COMPOUNDS AND DERIVATIVES THEREOF, WHEREIN AN ORGANOLEADMAGNESIUM HALIDE IS PREPARED FROM A GRIGNARD REAGENT (RMGX, WHEREIN R IS AN ORGANIC RADICAL AND X A HALOGEN) AND A LEAD HALIDE OR LEAD CARBOXYLATE AND THEN REACTED WITH AN ORGANIC POLYHALIDE TO FORM THE ALKYL LEAD COMPOUND.

United States Patent 3,644,450 METHOD OF MAKING ALKYL LEAD COMPOUNDS Shirl E. Cook and Kenneth C. Williams, Baton Rouge, La., assignors to Ethyl Corporation, New York, NY. No Drawing. Filed Aug. 7, 1969, Ser. No. 848,358

Int. Cl. C07f 7/24 US. Cl. 260-437 R 16 Claims ABSTRACT OF THE DISCLOSURE A method of making alkyl lead compounds and derivatives thereof, wherein an organoleadmagnesium halide is prepared from a Grignard reagent (RMgX, wherein R is an organic radical and X a halogen) and a lead halide or lead carboxylate and then reacted with an organic polyhalide to form the alkyl lead compound.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates broadly to the field of organolead compounds. It particularly relates to a method of making symmetrical and unsymmetrical organolead and di-lead compounds.

Description of the prior art Organolead compounds are especially valuable as antiknock compounds in gasoline. Tetraalkylleads, principally tetraethyllead and tetramethyllead, have been widely used commercially for such purpose. Most of the methods of making organolead compounds result in the formation of free lead, which is undesirable both from a handling standpoint and an economic standpoint.

One of the most widely used laboratory methods of preparing tetraalkyllead compounds (R Pb) is from the reaction of lead chloride (PbCl and an organomagnesium or other metal derivative (RM) in ether as follows:

heat 411M 2PbCl RrPb Pb 4MCl ether When using an alkyl magnesium halide, the foregoing equation encompasses the following steps:

Organolead metal compounds (R Pb-M) have been known for a number of years. Trialkylplumbylsodium and triarylplumbylsodium derivatives, triarylplumbyllithiums (namely, triphenylplumbyllithium) and triarylplumbylmagnesium bromides (namely trimesitylplumbylmagnesium bromide and triphenylplumbylmagnesium bromide) have been described in the literature. In 1939, H. Gilman and J. C. Bailie proposed the possible existence of a compound of the type R PbMgBr in the reaction of triethyllead bromide and magnesium metal to produce tetraethyllead. No trialkylplumbylmagnesium halides have been subsequently reported.

SUMMARY OF THE INVENTION It has been discovered that many new organolead compounds can be prepared using trialkylplumbylmagnesium halide compounds and organic polyhalides. The trialkylplumbylmagnesium halide compounds may be first syn- 3,644,450 Patented Feb. 22, 1972 "ice R:any organic radical R=any organic di-radical X=a halogen X=a halogen or carboxylate The reactions are carried out in the presence of a catalyst and/ or solvent which is an ether more basic than diethyl ether. Tetrahydrofuran (THF) is a preferred solvent and/ or catalyst.

The reaction is also carried out at a temperature of from about l0 C. to about 30 C. Low temperatures are preferred, and optimum results are obtained at a temperature of about 5 C.

The reaction may also be carried out in a one step reaction wherein a Grignard reagent and an organo polyhalide are mixed together in a catalyst or solvent and subsequently a lead halide or lead carboxylate is added to the mixture. This reaction is summarized as follows:

wherein R=any organic radical R=any organic di-radical X=a halogen X'=a halogen or carboxylate X"=a halogen or carboxylate The catalyst and the temperature conditions are the same as for the foregoing reactions.

It is a primary object of the present invention to provide a new and novel method of preparing lead alkyls and lead alkyl derivatives for use as gasoline antiknock compounds.

Another important object of the present invention is to provide a new and improved method of making organolead compounds wherein no by-product lead metal is formed.

Another principal object of the present invention is to provide new and unique organolead compounds.

Other objects and advantages of the present invention will become more readily apparent from a reading of the description and claims hereinafter.

DESCRIPTION OF THE PREFERRED EMBODIMENT In one preferred form of the invention an organoleadmagnesium chloride is prepared from a Grignard reagent (EtMgCl or 'MeMgCl) and lead chloride and then reacted with methylene chloride. The reaction is carried out using tetrahydrofuran (TI-IF) as a catalyst or solvent at a temperature of 5 C. The reaction steps may be summarized as follows:

( THF The reaction may also be carried out as a one step reaction as follows:

scmomM m 011,012 +2Pbo12 I reacting trialkylplumbylmagnesium chlorides with an organo polyhalide or an organo silicon halide and the yield thereof;

4 THE. To the solution was added ml. (excess) of methylene dichloride. The mixture was stirred at 5 C. for 15 minutes, 15 minutes at ambient temperature, and 10 minutes at 50 C. The greenish-brown color disappeared and a gelatinous precipitate (magnesium chloride-THF etherates) was formed. The mixture was hydrolyzed with 300 ml. of water and the THF was removed by distillation. The organolead product was separated and washed several times with water. An attempt was made to vacuum distill the product but considerable decomposition occurred. Purification was achieved by removing the volatile impurities by steam distillation. After separation 48.5 g. (81 percent) of colorless nondistillable product was obtained.

Analysis.Calcd. for C H Pb (percent): Pb, 68.75. Found (percent): Pb, 68.65.

Example II (Triethylplumbyl) (trimethylsilyl)methane. Triethylplumbyl-magnesium chloride was prepared from 16.0 g. (0.66 g.-atom) of magnesium, an equivalent amount of ethyl chloride and 55.6 g. (0.2 m.) of lead chloride at 5 The process of this invention and the new compounds produced thereby may be more completely understood and illustrated by the following examples.

GENERAL PROCEDURE All reactions were carried out under a nitrogen atmosphere. Tetrahydrofuran (THF) was distilled from lithium aluminum hydride before use. Anhydrous lead acetate was obtained by heating the trihydrate at 110 C. for several hours under a vacuum or removal of the water of hydration by azeotropic distillation with toluene.

The reactions were performed in a 500 ml. or 100 ml. three-necked round-bottom flask equipped with condenser (Dewar filled with Dry Ice-acetone) and magnetic or paddle stirrer. The lead salt was added from a 50 ml. round-bottom flask connected to the reaction vessel by a short piece of Gooch tubing. The Grignard reagents were prepared from magnesium turnings and a slight excess of the alkyl halide. The excess alkyl halide was then removed by heating at reflux for a few minutes under a nitrogen flush.

Lead contents of the new organolead derivatives were determined by reaction with bromine in carbon tetrachloride, destruction with nitric and perchloric acid and titration with EDTA to the endpoint using xylenol orange as indicator.

During the hydrolysis of the reaction mixtures enough dilute HCl was added to solubilize the precipitated magnesium salts.

Triethylplumbylmagnesium chloride or trimethylplumblymagnesium chloride was prepared as follows: A Grignard solution prepared from 8.0 g. (0.33 g.- atorn) of magnesium and an equivalent amount of methyl chloride or ethyl chloride in 400 ml. of THF was treated slowly at 5 C. with 27.8 g. (0.1 m.) of lead chloride. Greenishbrown and homogeneous solutions containing the complexes were obtained. Derivatives of the compounds were prepared as described in the examples hereinafter.

of magnesium, an equivalent amount of ethyl chloride and 55.6 g. (0.2 m.) of lead chloride at 5 C. in 900 ml. of

C. in 900 ml. of THF. To the solution was added 25 g. 0.2 m.) of chloromethyltrimethylsilane. The mixture was warmed to ambient temperature and stirred for 30 minutes and at 50 C. for 10 minutes. The mixture was hydrolyzed with 300 ml. of water and the THF was removed by distillation. The organolead product was separated from the aqueous layer and washed several times with water. Vacuum distillation gave 55.3 g. (73 percent) of colorless product boiling at 5759 C. (0.5 mm.).

Annlysis.-Calcd. for C H SiPb (percent): 'Pb, 54.29. Found (percent): Pb, 54.69.

Example III Bis(trimethylplumbyl)methane. Trimethylplumbylmagnesium chloride was prepared from 8.0 g. (0.33 g.- atom) of magnesium, an equivalent amount of methyl chloride and 27.8 g. (0.1 m.) of lead chloride at 50 C. in 400 ml. of THF. To the complex was added 15 ml. (excess) of methylene dichloride and the mixture was stirred for 30 minutes at 5 C. The ice bath was removed and the reaction mixture was warmed to 50 C. for 15 minutes. The greenish-brown color disappeared and a gelatinous precipitate was formed. The mixture was hydrolyzed with 300 ml. of water and the THF was removed by distillation. The organolead product was separated from the aqueous layer and washed several times with water. Vacuum distillation gave 21 g. percent) of colorless product boiling at 5759 C. (0.3 mm.).

Analysis.-Calcd. for C H Pb (percent): Pb, 79.92. Found (percent): Pb, 80.07.

Example IV (Trimethylplumbyl)(trimethylsilyl)methane.Trimethylplumbylmagnesium chloride was prepared from 8.0 g. (0.33 g. atom) of magnesium, an equivalent amount of methyl chloride and 27.8 g. (0.1 m.) of lead chloride as described above at 5 C. To the solution was added 12.2 g. (0.1 In) of chloromethyltrimethylsilane. The ice bath was removed and the solution was warmed to ambient temperature and stirred for 25 minutes. The greenishbrown color disappeared and a gelatinous precipitate was formed. The mixture was hydrolyzed with 300 ml. of water and the THF was removed by distillation. The heavy organolead product was separated from the aqueous layer and washed several times with water. Vacuum distillation gave 23.6 g. (70 percent) of colorless product boiling at 3435 C. (0.3 mm.).

Analysis.-Calcd. for C H SiPb (percent): Pb, 61.02. Found *(percent): Pb, 60.83.

Halogens suitable for use in the instant invention may be chlorine, bromine, and iodine.

Some examples of polyhalogenated hydrocarbons which may be used in preparing the unique organolead compounds of this invention are: 1,2-dichloroethane; 1,2-dichloropropane; 1,2 dichlorobutane; 2,3 dibromobutane; 1,2-diiodopentane; 1,4-dibromo-2-butene; 1,2-dibromopropane; 1,1-trichloropropanone; methylene chloride; methylene bromide; methylene iodide; chloroform; bromoform; iodoform; carbon tetrafluoride; carbon tetrachloride; carbon tetrabromide; dichlorodi-fluoromethane; ethylene dibromide; ethylidene chloride; ethylidene bromide; tetrachloroethane; hexachloroethane; dichloroethylene; trichloroethylene; trimethylene bromide; tetramethylene bromide; pentamethylene bromide; and hexamethylene bromide.

Carboxylates suitable for use in the instant invention are those having the formula RCOO, wherein R=hydrogen, alkyl group, halogen-substituted alkyl group, hydroxy-substituted alkyl group, oxy-substituted alkyl group, thio-substituted alkyl group, cyano-substituted alkyl group, glyoxy-substituted alkyl group, aryl group, ethylenic-su bstituted alkyl group, and carboxy acid-substituted alkyl group.

The products of this invention possess considerable utility. These compositions are soluble in hydrocarbons and are valuable as antiknock compositions for gasolines.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes may be made within the scope of the appended claims without departing from the spirit of the invention.

We claim:

1. A method of making lead alkyls comprising the steps of:

(a) reacting a Grignard reagent and a lead salt selected from the group consisting of lead chloride, lead bromide, lead iodide and lead carboxylates, said reaction being carried out in the presence of an ether more basic than diethyl ether,

(b) reacting the lead-magnesium salt from the previous reaction with a polyhalogenated lower alkyl hydrocarbon thereby forming a lead alkyl, said reaction being carried out in the presence of an ether more basic than diethyl ether.

2. The method of claim 1 wherein the reactions are carried out in the presence of tetrahydrofuran.

3. The method of claim 1 wherein the reactions are carried out at a temperature of from about C. to about 30 C.

4. The method of claim 1 wherein the reactions are carried out at a temperature of about 5 C.

5. A method of preparing lead alkyls, substantially in accordance with the following chemical reaction:

wherein:

R=a lower alkyl radical; R'=a lower alkyl di-radical; X=a halogen selected from the group consisting of chlorine, bromine and iodine; X'=a halogen selected from the group consisting of chlorine, bromine and iodine; X=a halogen selected from the group consisting of chlorine, bromine and iodine or carboxylate; E=an ether more basic than diethyl ether. 6. The method of claim 5 wherein said ether is tetrahydrofuran.

7. A method of preparing lead alkyls, substantially in 6 accordance with the following chemical reactions in the order set forth:!

(2) 2RaPbMgX RX2 i wherein:

R=a lower alkyl radical;

R'=a lower alkyl di-radical;

X=a halogen selected from the group consisting of chlorine, bromine or iodine;

X:a halogen selected from the group consisting of chlorine, bromine or iodine or carboxylate;

E=an ether more basic than diethyl ether.

8. The method of claim 7 wherein said ether is tetrahydrofuran.

9. A method of making lead alkyls, comprising the step of reacting a Grignard reagent, a lead salt selected from the group consisting of lead chloride, lead bromide, lead iodide and lead carboxylate and a polyhalogenated lower alkyl hydrocarbon, said reaction being carried out in the presence of an ether more basic than diethyl ether.

10. The method of claim 9, wherein said polyhalogenated lower alkyl hydrocarbon is selected from the group consisting of methylene dichloride, 1,2-dichloroethane, 1,1-dichloroethane, carbon tetrachloride, chloroform, 1,2-dichloropropane and 1,2-dichlorobutane.

11. The method of claim 9, wherein said polyhalogenated lower alkyl hydrocarbon is selected from the group consisting of methylene bromide, ethylene dibromide, bromoform and carbon tetrabromide.

12. The method of claim 9, wherein the halogen atoms in the polyhalogenated lower alkyl hydrocarbon are selected from the group consisting of chlorine and bromine.

13. A method of making lead alkyls, comprising the step of reacting a Grignard reagent, lead chloride or lead acetate and a polyhalogenated lower alkyl hydrocarbon, said reaction being carried out in the presence of an ether more basic than diethyl ether.

14. The method of claim 13, wherein said polyhalogenated lower alkyl hydrocarbon is selected from the group consisting of methylene dichloride, 1,2-dichloroethane, 1,1-dichloroethane, 1,2-dichloropropane, 11,2-dichlorobutane, carbon tetrachloride and chloroform.

15. The method of claim 13, wherein said polyhalogenated lower. alkyl hydrocarbon is selected from the group consisting of methylene bromide, ethylene dibromide, bromoform and carbon tetrabromide.

16. The method of claim 13, wherein the halogen atoms in the polyhalogenated lower alkyl hydrocarbon are selected from the group consisting of chlorine and bromine.

References Cited UNITED STATES PATENTS OTHER REFERENCES Glockling et 3.1., J. Chem. Soc. (1961), pp. 4405-09. Shapiro et al., The Organic Compounds of Lead, Interscience Publishers, John Wiley & Sons, New York, pp.

Applicants Citation Gilman et al., J. Amer. Chem. Soc., vol. 61, pp. 73 1- 738 1939 JAMES E. POER, Primary Examiner H. M. S. SNEED, Assistant Examinen 

